Numerous methods for removal of acid gas from gas mixtures containing the same and recovering purified hydrogen gas are well known in the art and in commercial practice. Included among the known processes for acid gas removal from gaseous streams are those employing physical absorption of CO2 and/or H2S as distinguished from other processes involving chemical reaction. Typical apparatuses required for conversion of sour synthesis gas from a shift or hydrolysis reactor into hydrogen in a hydrogen and/or ammonia producing gasification plant includes an acid gas removal unit for removal of acid gas components like H2S, COS and CO2 typically based by a physical solvent wash, e.g. UOP SeparALL™ process or UOP Selexol™ process. Alternatively, UOP Amine Guard™ FS Process may be used for the removal of acid gas components. This is required to meet the quality requirement of the synthesis gas feed to the downstream process to obtain purified hydrogen gas. Further, the apparatus includes a hydrogen purification unit which may use membrane technology, e.g. UOP Polysep™ membranes and/or Pressure Swing Adsorption (PSA) technology (e.g. UOP Polybed™ PSA Technology). High-purity hydrogen is needed in a variety of refinery and petrochemical processes. Further, destruction of CO, H2 and other components presented in the CO2 stream from acid gas removal unit may occur through systems including thermal or catalytic oxidizers. This is required to meet CO2 quality requirements for further use.
A typical process and apparatus as described above requires a lot of steam consumption. Further, a significant amount of external fuel gas is required in the thermal oxidizer to provide the CO2 rich gas stream. Moreover, there are significant challenges faced in increasing the amount of on-spec hydrogen gas in such hydrogen-producing gasification plants having the acid gas removal, thermal oxidizer and pressure swing adsorption units. Also, a significant amount of tail gas from the PSA bed is being directed to location outside the plant.
Accordingly, it is desirable to provide an improved process and apparatus for conversion of synthesis gas into hydrogen. Further, it is desirable for the instant apparatus and process to be a net steam producer rather than a steam consumer. Moreover, it is desirable to minimize the consumption of external fuel gas in the thermal oxidizer unit in such apparatuses. Additionally, it is desirable to increase the amount of purified hydrogen being produced from the synthesis gas. Furthermore, other desirable features and characteristics of the present subject matter will become apparent from the subsequent detailed description of the subject matter and the appended claims, taken in conjunction with the accompanying drawing and this background of the subject matter.